Wavelength-division multiplex system and a method of automatically setting conversion wavelengths of such a system

ABSTRACT

For a WDM device including a multiplexer receiving fixed wavelengths, wavelength-converting parts for converting input wavelengths from optical transmission devices into the fixed wavelengths, and interface parts provided between the multiplexer and the wavelength-converting parts and having a specific wavelength that matches the fixed wavelength of the multiplexing part, a method and a device is provided for automatically determining the specific wavelength of the interface part that is to be selected as a converted wavelength output from the wavelength-converting part.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wavelength-division multiplex systemthat enables an efficient use of optical fibers and particularly to animproved method of setting wavelengths to be allocated to eachtransmission channel in such a wavelength-division multiplex system.

Recently, optical transmission systems provided with lines with largercapacity are being developed. Wavelength-division multiplexing (WDM)technology is becoming of an interest as a technology that is necessaryfor making efficient use of optical fibers.

FIG. 1 is a diagram showing an example of a WDM system. In the exampleshown in FIG. 1, the WDM system includes two WDM devices connected toeach other. Each of the WDM devices includes a wavelength-convertingunit (λ-converter) 110, a wavelength interface unit (I/F) 120 and awavelength multiplexer/demultiplexer (MUX/DEMUX) 130. Thewavelength-converting unit 110 receives signals of wavelength λs fromdownstream optical transmission devices 200-1 through 200-n and convertsthe wavelength λs into wavelengths λ1 through λn that are to be used onthe upstream side of the wavelength-converting unit 110, or, used by thewavelength interface unit 120. In order to perform such a convertingoperation, the wavelength-converting unit 110 is configured usingwavelengths λ1 through λn that correspond to channels of the wavelengthinterface unit 120. The wavelength interface unit 120 is provided withchannels with predetermined wavelengths λ, i.e., λ1 through λn, that arefixed to and individually usable for the corresponding input terminalsof the MUX/DEMUX 130 connected thereto. It is to be noted that in thefollowing text, “upstream” is to be understood as a position along thetransmission path nearer to the MUX/DEMUX 130 side and “downstream” isto be understood as a position along the transmission path nearer to theoptical transmission devices 200-1, . . . , 200-n.

Signals of wavelengths λ1 through λn that are output from upstreamoutput terminals of the wavelength interface unit 120 are received andmultiplexed by the MUX/DEMUX 130. The multiplexed signals aresimultaneously transmitted through an optical fiber. Then, themultiplexed signals are transmitted to an opposing receiving-side WDMdevice in which the MUX/DEMUX 130 demultiplexes the multiplexed signalsback to original signals. In this manner, the optical fiber can be usedwith improved efficiency.

Currently, the WDM device is not capable of multiplexing a plurality ofsignals of the same wavelength λ. Therefore, wavelengths λ of thesignals should be set at the wavelength-converting unit 110 such thatthe wavelengths λ of the signals received at the MUX/DEMUX 130 do notoverlap with each other.

In order to set wavelengths λ at the wavelength-converting unit 110, theoperator needs to know available wavelengths λ and set differentwavelengths λ for each of the channels to be multiplexed. Therefore, awavelength-setting operation is burdensome for the operator. Also, it isexpected that the numbers of channels to be multiplexed will increase inthe future. For at least the reasons described above, there is a needfor a method of facilitating the wavelength-setting operation for awavelength-multiplexing process.

2. Description of the Related Art

FIG. 2 is a diagram showing an example of a WDM device of the relatedart. Herein, “upstream” is to be understood as a position nearer to theMUX/DEMUX 130 side and “downstream” is to be understood as a positionnearer to the optical transmission devices 200-1, . . . , 200-n. In thisexample, upstream input terminals of the wavelength-converting unit 110are capable of receiving a plurality of different wavelengths λ.Therefore, it is not necessary to set wavelengths λ for transmissionsfrom downstream output terminals of the wavelength interface unit 120 tothe upstream input terminal of the wavelength-converting unit 110. Onthe other hand, each of the downstream input terminals of the wavelengthinterface unit 120 is configured to receive a fixed wavelength λ foreach channel. Therefore, the operator no longer needs to set wavelengthsλ for transmission from the upstream output terminals of thewavelength-converting unit 110 and the downstream input terminals of thewavelength interface unit 120.

For each of channels of the wavelength-converting unit 110, a range ofwavelength λ that can be configured (configurable λ-range) ispredetermined. Therefore, the operator needs to configure a wavelength λof each channel on the basis of a wavelength λ that can be used atwavelength interface subunits of the wavelength interface unit and on apredetermined range of wavelength λ that can be set in thewavelength-converting unit 110 connected to the wavelength interfaceunit 120 via an optical fiber. The wavelength λ is, for example,configured in a manner described below (see FIGS. 3, 4A and 4B).

The operator operates a control part 121 of the wavelength interfaceunit 120 to input a request for causing the wavelength interface unit120 to change into an operating state (step S1).

The operator looks up for wavelength λ that can be received by thewavelength interface subunits of the wavelength interface unit 120 thatis to be set up (step S2).

The operator looks up for a range of the wavelength λ that can beconfigured (configurable range) to the wavelength-converting subunits ofthe wavelength-converting unit 110 connected to the correspondingwavelength interface subunits of the wavelength interface unit 120 (stepS3).

The operator specifies wavelength λ and sends a request to the controlpart 111 of the wavelength-converting unit 110 for setting the specifiedwavelength λ (step S4).

The control part 111 searches for the specified wavelength λ in theconfigurable λ-range (step S5).

It is determined whether the specified wavelength λ is in theconfigurable λ-range and can be output as a wavelength λ of the relevantwavelength-converting subunit of the wavelength-converting unit 110(step S6).

If it is determined that the specified wavelength λ cannot be output(step S6, NO), an NG signal is sent to inform the operator that thespecified λ cannot be set. Then, steps S2 to S5 are repeated.

If it is determined that the specified wavelength λ can be output (stepS6, YES), an OK signal is sent to the operator to inform that thespecified λ can be set. Then, the operator sets the specified λ as awavelength λ for the relevant wavelength-converting subunit of thewavelength-converting unit 110 and sends main signals to the wavelengthinterface unit 120 using the specified λ (step S7).

The operator confirms whether optical transmission, or the main signal,using the specified wavelength λ is received at the wavelength interfaceunit 120 (step S8).

If reception of the optical transmission is confirmed, the wavelengthsetting operation is terminated. If reception of the opticaltransmission is not confirmed, steps S2 to S8 are repeated.

Steps S1 to S8 are repeated for each channel.

There are several drawbacks with such a wavelength-setting operation ofthe related art.

First, since each of the downstream input terminals of the wavelengthinterface unit 120 can receive a fixed wavelength, the operator needs tosearch for a usable wavelength λ. If the operator mistakenly sets thewavelength λ, the data cannot be transmitted and a setting operation ofthe wavelength λ must be performed again.

Second, the wavelength-setting operation of the related art requiresmany steps of complicated manual operations by the operator. This mayresult in man-caused erroneous operations.

Third, according to the wavelength setting operation of the related art,wavelength setting should be repeated for a number of channels to bemultiplexed. Therefore, it requires considerable efforts by theoperator.

Fourth, according to the wavelength setting operation of the relatedart, the operator is not informed of alteration of connected channels.Therefore, the user may try to transmit signals using an erroneouslyspecified wavelength. In such a case, data cannot be transmitted untilthe operator becomes aware of the error and reconfigures the wavelength.

SUMMARY OF THE INVENTION

Accordingly, it is a general object of the present invention to providea WDM device in which a process of setting wavelengths λ forwavelength-converting parts can be performed without manual operations.

It is another and more specific object of the present invention toprovide a WDM device in which information of the channel-specificwavelength of the interface part between the multiplexer and thewavelength-converting part is supplied to the wavelength-convertingpart.

According to the present invention, a wavelength-division multiplexing(WDM) device is provided which includes: a multiplexing part having aplurality of input terminals that are capable of receiving fixedwavelengths, respectively, and an output terminal, the fixed wavelengthsbeing multiplexed onto a multiplexed signal and output via the outputterminal; a plurality of wavelength-converting parts each connected toan optical transmission device so as to convert an input wavelength fromthe optical transmission device into a converted wavelengthcorresponding to the fixed wavelength; and a plurality of interfaceparts each connected between the input terminal of the multiplexing partand the wavelength-converting part, the interface part having a specificwavelength that matches the fixed wavelength of the input terminal ofthe multiplexing part.

According to one embodiment, the interface part is provided with afilter that allows the specific wavelength to pass through and anencoder/modulator that encodes and modulates the filtered signal into apattern specific to the interface part. The specific wavelength of theinterface part is detecting by sequentially altering the convertedwavelength, analyzing wavelengths of the multiplexed signal to detectthe encoded and modulated signal wherefrom the pattern specific to theinterface part is obtained and identifying the interface part and itsspecific wavelength.

According to another embodiment, the interface part encodes andmodulates an optical signal in a pattern specific to its specificwavelength and transmits the encoded and modulated optical signal to thewavelength-converting part connected thereto. The specific wavelength ofthe interface part is detected by reading the specific wavelength from amodulated component of the encoded and modulated optical signal.

According to a further embodiment, the specific wavelength of theinterface part is detected by the interface part transmitting opticalsignals of its specific wavelength to the wavelength-converting partconnected thereto, and the wavelength-converting part analyzing thewavelength of the transmitted optical signal to detect the specificwavelength of the interface part.

According to a further embodiment, the specific wavelength of theinterface part is determined by the interface part transmitting opticalsignals of its specific wavelength to the wavelength-converting partconnected thereto, and the optical signals of the specific wavelengthbeing supplied to a variable wavelength filter provided in thewavelength-converting part while varying the pass-band wavelength of thevariable wavelength filter so as to obtain the pass-band wavelength ofthe filter when the optical signal is allowed to pass through.

According to a further embodiment, the plurality of interface partssimultaneously generate and output a plurality of signals with differentwavelengths, respectively, by wavelength conversion. Each of theinterface parts is provided with a filter that only allows a signalhaving its specific wavelength to pass through.

Also, methods of automatically setting a converted wavelength outputfrom each of a plurality of wavelength-converting parts of awavelength-division multiplexing (WDM) device are provided.

With the WDM devices and methods described above, erroneous setting ofwavelength λ can be prevented. Also, since the operator's interventionis reduced, reliability of the wavelength setting operation can beimproved. Also, troublesome operation is reduced and convenience of theoperation is improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a general structure of a WDM system;

FIG. 2 is a block diagram of a WDM device of the related art;

FIG. 3 is a flowchart showing process steps of an operation of the WDMdevice of the related art;

FIGS. 4A and 4B are operational sequence diagrams showing an operationof setting wavelength at a wavelength-converting unit of the WDM deviceof the related art;

FIG. 5 is a general configuration diagram showing the WDM device of thepresent invention;

FIG. 6 is a block diagram showing a WDM device of a first embodiment ofthe present invention;

FIG. 7 is a flowchart showing process steps of an operation of a WDMdevice of the first embodiment of the present invention;

FIG. 8 is a diagram showing time-charts of an example of a mode ofmodulation of optical signals that can be applied to the WDM device ofthe first embodiment of the present invention;

FIG. 9 is a diagram showing time-charts of an example of another mode ofmodulation of optical signals that can be applied to the WDM device ofthe first embodiment of the present invention;

FIG. 10 is a block diagram showing a WDM device of a second embodimentof the present invention;

FIG. 11 is a flowchart showing process steps of an operation of a WDMdevice of the second embodiment of the present invention;

FIG. 12 is a block diagram showing a WDM device of a third embodiment ofthe present invention;

FIG. 13 is a flowchart showing process steps of an operation of a WDMdevice of the third embodiment of the present invention;

FIG. 14 is a block diagram showing a WDM device of a fourth embodimentof the present invention;

FIGS. 15A and 15B are diagrams showing time-charts of examples of modesof modulation of optical signals that can be applied to the WDM deviceof the fourth embodiment of the present invention;

FIG. 16 is a diagram showing time-charts of an example of another modeof modulation of optical signals that can be applied to the WDM deviceof the fourth embodiment of the present invention;

FIG. 17 is a diagram showing time-charts of an example of still anothermode of modulation of optical signals that can be applied to the WDMdevice of the fourth embodiment of the present invention;

FIG. 18 is a block diagram showing a WDM device of a fifth embodiment ofthe present invention;

FIG. 19 is a diagram showing time-charts of an example of a mode ofmodulation of optical signals that can be applied to the WDM device ofthe fifth embodiment of the present invention;

FIGS. 20A and 20B are diagrams showing time-charts of examples of othermodes of modulation of optical signals that can be applied to the WDMdevice of the fifth embodiment of the present invention;

FIG. 21 is a diagram showing time-charts of an example of still anothermode of modulation of optical signals that can be applied to the WDMdevice of the fifth embodiment of the present invention;

FIG. 22 is a diagram showing time-charts of an example of yet anothermode of modulation of optical signals that can be applied to the WDMdevice of the fifth embodiment of the present invention;

FIG. 23 is a diagram showing time-charts of an example of yet anothermode of modulation of optical signals that can be applied to the WDMdevice of the fifth embodiment of the present invention;

FIG. 24 is a block diagram showing a WDM device of a sixth embodiment ofthe present invention;

FIG. 25 is a block diagram showing a WDM device of a variant of thesixth embodiment of the present invention;

FIG. 26 is a block diagram showing a WDM device of a seventh embodimentof the present invention;

FIG. 27 is a block diagram showing a WDM device of a variant of theseventh embodiment of the present invention;

FIG. 28 is a block diagram showing a WDM device of an eighth embodimentof the present invention;

FIG. 29 is a block diagram showing a WDM device of a variant of theeighth embodiment of the present invention;

FIG. 30 is a block diagram showing a WDM device of a ninth embodiment ofthe present invention;

FIG. 31 is a flowchart showing process steps of an operation of a WDMdevice of the ninth embodiment of the present invention;

FIG. 32 is a flowchart showing another example of process steps of anoperation of a WDM device of the ninth embodiment of the presentinvention;

FIG. 33 is a block diagram showing a WDM device of a variant of theninth embodiment of the present invention;

FIG. 34 is a block diagram showing a WDM device of a tenth embodiment ofthe present invention;

FIG. 35 is a flowchart showing process steps of an operation of a WDMdevice of the tenth embodiment of the present invention;

FIG. 36 is a flowchart showing another example of process steps of anoperation of a WDM device of the tenth embodiment of the presentinvention;

FIG. 37 is a block diagram showing a WDM device of an eleventhembodiment of the present invention; and

FIG. 38 is a flowchart showing process steps of an operation of a WDMdevice of the eleventh embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, principles and embodiments of the present inventionwill be described with reference to the accompanying drawings.

FIG. 5 is a diagram showing a basic configuration of awavelength-converting unit 110 and a wavelength interface unit 120 of aWDM (Wavelength-Division Multiplexing) system of the present invention.Herein, “upstream” is to be understood as a position nearer to theMUX/DEMUX 130 side and “downstream” is to be understood as a positionnearer to the optical transmission devices 200-1, . . . , 200-n. In anexample shown in FIG. 5, “upstream” refers to the left-hand side of eachbox and “downstream” refers to the right-hand side of each box.

The wavelength interface unit 120 includes wavelength interface subunitsB1 through Bn (n is an integer greater than one) each having output andinput terminals on each of the downstream and upstream sides. Each ofthe wavelength interface subunits B1, . . . , Bn has an individually andfixedly usable optical wavelength. Wavelength information indicatingwavelengths of the wavelength interface subunits B1, . . . , Bn isreferred to as “channel-specific λ information” and is stored in thewavelength interface unit 120. Herein after, optical wavelength isgenerally denoted as “λ” and individually and fixedly usable opticalwavelengths for the wavelength interface subunits are denoted by “λ1, .. . , λn.”

The wavelength-converting unit 110 includes wavelength-convertingsubunits A1 through An, each of which may be set with a wavelength λthat corresponds to a channel-specific wavelength of one of thewavelength interface subunits B1, . . . , Bn. With the wavelength λbeing set, the wavelength-converting unit 110 converts a wavelength usedon its downstream side, hereinafter referred to as λs, into wavelengthsλ1, . . . , λn that are used on its upstream side. The downstream sideinput/output terminals of the wavelength interface subunits B1, . . . ,Bn are connected to the upstream side output/input terminals of thewavelength-converting subunits A1, . . . , An, respectively. Such astate may be, hereinafter described using a term “opposed” or alternateforms thereof. According to the present invention, wavelength λs of thesignal input into the wavelength-converting unit 110 from its downstreamside can be converted into the wavelengths λ1, . . . , λn used on itsupstream side, without requiring manual operation by the operator. Inother words, a setting operation of wavelengths, i.e., λ-setting, can beperformed automatically.

Various embodiment of the present invention will be described below.

FIG. 6 is a block diagram showing a configuration of the WDM device ofthe first embodiment of the present invention. As shown in the figure,the WDM device includes the wavelength-converting unit 110, thewavelength interface unit 120 and the MUX/DEMUX 130. Thewavelength-converting unit 110 is connected to optical transmissiondevices so as to receive signals to be multiplexed and to convertwavelengths of the received signals. The wavelength interface unit 120performs ON/OFF control of the signals received from thewavelength-converting unit 110 at predetermined timings. The MUX/DEMUX130 multiplexes the plurality of signals from the wavelength interfaceunit 120 and transmits the multiplexed signals to an optical fiber. TheMUX/DEMUX 130 may be replaced by a multiplexer if the WDM device is onlyused for transmitting signals.

FIG. 6 shows that the wavelength-converting unit 110 includes thewavelength-converting subunits A1, . . . , An, each converting thewavelength of the signal received from corresponding optical device ofeach channel and outputting the converted signal to the wavelengthinterface unit 120. It is also shown that the wavelength interface unit120 includes wavelength interface subunits B1, . . . , Bn, each couplingthe signals from the corresponding wavelength-converting subunits A1, .. . , An, to the corresponding downstream input terminal of theMUX/DEMUX 130 for each channel.

The wavelength-converting subunits A1, . . . , An output signals in sucha manner that the wavelength λ is varied at a predetermined intervalunder control of the control part 111. A program for causing such anoperation may be stored for this purpose. Each of the wavelengthinterface subunits B1, . . . , Bn is provided with a filter 122 thatallows signals having a wavelength λ that matches the fixedly andindividually predetermined channel-specific wavelength λ of thewavelength interface subunits B1, . . . , Bn to pass through. In thefollowing text, one of the wavelength-converting subunits A1, . . . , Anis generally denoted by “Ax” and the corresponding wavelength interfacesubunit B1, . . . , Bn is generally denoted by “Bx”.

In order to perform λ-analysis to verify, even after being multiplexedby the MUX/DEMUX 130, that the signals from the upstream terminal of Bxis actually output via the MUX/DEMUX 130, the wavelength interfacesubunit Bx is further provided with a first encoder/modulator (ON/OFFcontrol) part 123 at a position upstream of the filter 122. The firstencoder/modulator part 123 switches its output signal between ON and OFFstates to transmit channel number information of the correspondingwavelength interface subunit Bx to the upstream side (MUX/DEMUX 130side) in the form an ON/OFF signal, or, a modulated signal (binaryvalues expressed by “0” and “1”). Further, a λ-analyzer 140 is providedat a position upstream of an amplifier 150 that is at a positionupstream of the MUX/DEMUX 130. ON/OFF patterns are predetermineduniquely for the wavelength interface subunits B1, . . . , Bn,respectively. Thus, by detecting the ON/OFF patterns at the λ-analyzer140 after the signals are being multiplexed, it is verified that thesignals of the relevant channel has passed through the MUX/DEMUX 130. Itis to be noted that the signal having the relevant ON/OFF pattern istransmitted to the MUX/DEMUX 130 side, i.e., upstream side, only if thesignal from the optical transmission device has been allowed to passthrough the filter 122.

If the λ-analyzer 140 detects that the DATA signals from the wavelengthinterface subunit Bx are being output from the MUX/DEMUX 130, this isreported to the relevant wavelength interface subunit Bx.

Further, a second encoder/modulator (ON/OFF control) part 124 isprovided in each of the wavelength interface subunits Bx for checkingsignals that are output from each of the wavelength-converting subunitsAx of the wavelength-converting unit 110. It is determined whether thewavelength λ of the signals transmitted from the wavelength-convertingsubunit Ax to the corresponding wavelength interface subunit Bx of thewavelength interface unit 120 matches the channel-specific wavelength λthat has been fixedly allocated to the relevant wavelength interfacesubunit Bx. An OK/NG signal is produced by controlling the ON/OFF stateof the signal and the OK/NG signal is transmitted from the downstreamterminal of the wavelength interface subunit Bx to the relevantwavelength-converting subunit Ax.

An operation of the first embodiment of the present invention will bedescribed with reference to a flowchart of FIG. 7.

The following description relates to a process of automatically settinga wavelength λx-A set for signals that are output from the upstreamterminal of the wavelength-converting subunit Ax of thewavelength-converting unit 110. Requirements for the process describedbelow are that the wavelength interface unit 120 is in its operationalstate, that the wavelength-converting unit 110 and the wavelengthinterface unit 120 are arranged so as to oppose each other, and that itis not necessary that the main signals are communicated from thewavelength interface unit 120 to the wavelength-converting unit 110.

In step 21, the operator inputs a DATA output request forwavelength-converting subunit Ax into the control part 111 of thewavelength-converting unit 110 in order to request thewavelength-converting subunit Ax to output signals to the wavelengthinterface subunit Bx. The wavelength-converting subunit Ax correspondsto a channel that is to undergo a wavelength-setting operation(λ-setting).

In step 22, the control part 111 of the wavelength-converting unit 110selects a wavelength λ to be set from a first storage part 113 in whichconfigurable wavelengths λ that can be output are stored. The specifiedλ is stored in a variable “lambda_temp”.

In this manner, the wavelength-converting unit 110 sets the wavelength λas (λ1-A) and transmits (or optically transmits) the signal λ1-A from anupstream output terminal of the wavelength-converting subunit Ax to adownstream input terminal of the corresponding wavelength interfacesubunit Bx (step S23).

The first encoder/modulator part 123 of the relevant wavelengthinterface subunit Bx generates channel position information by formingeither one of the two types of coded signals from the received signal.Th channel position information is transmitted to the MUX/DEMUX 130(step S24).

The λ-analyzer 140 measures the wavelength λ of the received signal(step S25).

The control part 121 of the wavelength interface unit 120 receives themeasured λ-information from the λ-analyzer 140 and stores it in avariable “lambda_measured”. Also, the control part 121 reads out thechannel position information (modulated information) of the measuredwavelength λ (step S26).

Further, the control part 121 makes an access to a λ-information storagepart 126 of the corresponding channel part Bx and retrieves informationindicating the wavelength λ that corresponds to the channel indicated bythe channel position information read out in step S25. The retrievedwavelength is stored as a variable “lambda_temp2”. Then, it isdetermined whether there is a match between the λ-information obtainedin step S25 and the λ-information obtained in step S26 (steps S29 andS30). In detail, in step S29, a predetermined allowable range λ is addedto the measured λ-information “lambda_measured”, as follows:lambda_(—) s=lambda_measured×(1−k)lambda_(—) l=lambda_measured×(1+k).

Then, in step S30, it is determined whether the λ-informationlambda_temp2 that is unique to the wavelength interface subunit Bx readfrom the wavelength interface subunit Bx is within the allowable range.That is to say, it is determined whether:

-   -   lambda_s<lambda_temp2, and,    -   lambda_temp2<lambda_l.

The control part 121 of the wavelength I/F unit 120 sends either an OKnotification request or a NG notification request depending on the valueof lambda_temp2 and the timeout condition.

If lambda_temp2 is within allowable range (step S30, YES), the controlpart 121 sends an OK notification request to the secondencoder/modulator part 124 of the relevant wavelength interface subunitBx (step S33). Also, a halt request is sent to the firstencoder/modulator part 123 of the relevant wavelength interface subunitBx (step S32).

If lambda_temp2 is not within the allowable range (step S30, NO) or apredetermined period of time has elapsed after initiating a data outputoperation from the downstream input terminal of the relevant wavelengthinterface subunit Bx (step S27, YES), an NG notification request is sentto the second encoder/modulator part 124 of the relevant wavelengthinterface subunit Bx (step S31).

Then, the second encoder/modulator part 124 generates either an OKsignal or an NG signal (see FIG. 9) depending on the OK/NG notificationrequest generated in steps S31 and S31. The generated OK signal or NGsignal is transmitted from the downstream output terminal of therelevant wavelength interface subunit Bx to the upstream input terminalof the corresponding wavelength-converting subunit Ax (step S34).

Upon reception of an OK signal at wavelength-converting subunit Ax (stepS35, OK), the data processing part 112 of the wavelength-convertingsubunit Ax sets the currently output wavelength value λ to itstransmitter part as a conversion wavelength (step S36).

Upon reception of an NG signal at the wavelength-converting subunit Ax(step S35, NG), the data processing part 112 of thewavelength-converting subunit Ax sends a resetting request to thecontrol part 111. In response, the control part 111 reselects a newwavelength λ from the first storage part 113 and rewrites the variablelambda_temp with the reselected wavelength λ (step S22). The lambda_tempinformation is transmitted to the corresponding wavelength interfacesubunit Bx (step S23). In this manner, steps S22 through S35 arerepeated until the value of the wavelength to be set λ is determined.

Steps S21 through S36 are repeated for a number of times correspondingto the predetermined number of channels.

It is to be noted that, according to this embodiment, the operation maybe performed while signals are being transmitted through other channels.In such a case, the control part 121 controls the encoder/modulator 123of the wavelength I/F part Bx to modulate a particular wavelength usingON/OFF states. The modulated particular wavelength may be specified byan analysis at the λ-analyzer 140.

FIG. 8 is a diagram showing an example of the channel positioninformation. In this case, modulation using ON/OFF states is performedusing number of pulses within a predetermined length of time period. Forexample, in order to express a channel position (channel number) three,pulsed codes indicating “0”, “0”, and “3” are generated in a sequentialmanner.

FIG. 9 is a diagram showing an example of the OK/NG signal. In theexample illustrated in the figure, an OK signal is represented by apulse having a longer period for an ON state and an NG signal isrepresented by a pulse having a shorter period for an ON state.

A second embodiment of the present invention will be described below.

FIG. 10 is a diagram showing a WDM device of the second embodiment ofthe present invention. In this embodiment, as shown in the figure, thewavelength-converting unit 110 is further provided with a retry countmonitoring part 114. A retry determination part 115 is provided in eachof the wavelength-converting subunits Ax. An operation of the secondembodiment will be described with reference to the flowchart shown inFIG. 11.

It is to be noted that operational requirements of the second embodimentare the same as those of the first embodiment.

In a similar manner to the first embodiment, the operator inputs a DATAoutput request to the control part 111 of the wavelength-converting unit110 (step S41). Then, a trial counter (retry_count) is initialized (stepS42).

Thereafter, while performing the process of FIG. 7, the retrydetermination part 115 of the wavelength-converting subunit Ax monitorsthe data-processing part 112. If the process of FIG. 7 (steps S22through S35) has failed for all the available wavelengths λ (step S44,YES), the trial counter is incremented and a retry request is sent tothe control part 111 (step S45).

The control part 111 returns to the process shown in FIG. 7, selects oneof the wavelength λ from the first storage part 113 (step S22), andrepeats the remaining process steps (steps S22 through S35).

The retry count monitoring part 114 monitors the retry determinationpart 115. When the trial counter exceeds a predetermined value k(retry_count>k), the operator is informed that automatic setting hasfailed, or, there is an abnormality. Such failure information containsinformation items such as the channel number and a cause of failure,e.g., “no wavelength λ is available for setting” (step S47). Then, theprocess is terminated.

It is to be noted that if data transmission of a signal having awavelength λ from the upstream output terminal of thewavelength-converting subunit Ax to the downstream input terminal of thewavelength interface subunit Bx has failed for some reason, even in acase where the signal is of a wavelength λ to be set, the wavelengthinterface unit 120 will determine that the wavelength λ cannot be set.Therefore, even if it is determined that all the wavelengths λ cannot beset, it is worth retrying.

A third embodiment of the present invention will be described below.

FIG. 12 is a diagram showing a WDM device of the third embodiment of thepresent invention. In this embodiment, as shown in the figure, thewavelength-converting unit 110 is further provided with a third storagepart 116 for storing wavelengths λ that has already been set. Anoperation of the second embodiment will be described with reference tothe flowchart shown in FIG. 11. An operation of this embodiment will bedescribed with reference a flowchart shown in FIG. 13.

It is to be noted that operational requirements of the third embodimentare the same as those of the first embodiment.

Upon initializing the wavelength-converting unit 110, a third storagepart 116 is initialized (step S51).

At the wavelength-converting subunit Ax, a relevant wavelength λx isautomatically determined in accordance with the process shown in FIG. 7(steps S52 through S55).

The determined wavelength λx is stored in the third storage part (stepS56).

Upon setting wavelength λ for the next wavelength-converting subunitAx+1, when selecting one of the wavelengths λ from the first storagepart 113, it is determined whether the selected wavelength λ has alreadybeen stored in the third storage part (step S53).

If in step S53, it is determined that the selected wavelength λ isstored in the third storage part 116, the process of FIG. 7 is performedfor the selected wavelength.

If in step S53, it is determined that the selected wavelength λ hasalready been stored in the third storage part 116, the selectedwavelength λ is discarded and a new wavelength λ is selected from thefirst storage part 113. Then, the processes of steps S53 through S55 arerepeated.

According to such an embodiment, it is possible to prevent any retryoperations for the “already set wavelength λ” for other channels in asimple manner. Accordingly, the process can be performed efficiently.

A fourth embodiment of the present invention will be described withreference to FIGS. 14, 15, 16 and 17.

FIG. 14 is a block diagram showing a fourth embodiment of the presentinvention and FIGS. 15 through 17 are diagram showing time charts ofencoded signals (modulated signals) that can be used in the fourthembodiment.

Requirements for the fourth embodiment are that thewavelength-converting and wavelength interface units 110 and 120 are inan operable state, that the wavelength-converting and wavelengthinterface units 110 and 120 are in a mutually opposed state, and thatdata transmission from the wavelength interface unit 120 to thewavelength-converting unit 110 may be stopped.

According to the fourth embodiment, an optical signal modulation isperformed on the channel-specific λ-information of the wavelength I/Fsubunit Bx. The modulated channel-specific λ-information is transmittedfrom the wavelength interface subunit Bx of the wavelength interfaceunit 120 to the wavelength-converting subunit Ax of thewavelength-converting unit 110. The wavelength-converting subunit Axsets the wavelength λ using the transmitted λ-information. Thisoperation will be described in detail.

First, the operator inputs to the wavelength interface subunit Bx arequest for changing from an idle state to an operational state. Therequest may include parameters such as device name, channel name andstate of operation. This is analyzed at the control part 121 of thewavelength interface unit 120. In response, a λ-setting request is sentto a third encoder/modulator part 127. Then, the third encoder/modulatorpart 127 reads the channel-specific λ-information of the relevantwavelength interface subunit Bx.

Then, the third encoder/modulator part 127 controls ON/OFF states of adownstream transmitter part TX of the wavelength interface subunit Bx togenerate and transmit START DATA. Then, the third encoder/modulator part127 performs encoding modulation (see FIGS. 16 and 17) of intensity ofan optical signal of wavelength λ (e.g., 1528.77) that has been readfrom the second information storage part 126. In this manner,λ-information is generated. The START DATA and the λ-information dataserve as follows. These data are generated by controlling the intensityof an optical signal to produce ON (signal continued) state and an OFF(signal intermitted) state (see FIG. 15A) such that codes can beexpressed by combinations of the ON/OFF states. As a variant, it is alsopossible to generate a LONG state and a SHORT state by controlling theperiod of the high-state of the light intensity and to express codeswith combinations of the LONG and SHORT states (see FIG. 17).

Then, the λ-information data is transmitted to the upstream receiverpart RX of the wavelength-converting subunit Ax. After the transmissionprocess of the λ-information, the third encoder/modulator part 127controls ON/OFF states of the downstream transmitter part TX of thewavelength interface subunit Bx so as to produce and transmit apredetermined END DATA (see FIGS. 16 and 17).

The upstream receiver part RX of the corresponding wavelength-convertingsubunit Ax receives the λ-information data. In the data processing part112, the λ-information is read out from the received λ-information data.The λ-information is sent to the control part 111. The control part 111looks up the first storage part 113 to determine whether the receivedλ-information is within the range of wavelength λ that can be set. If amatching wavelength λ exists in the first storage part 113, the-information is set to the downstream transmitter part TX of thewavelength-converting subunit Ax and the operator is informed ofcompletion of the setting operation. If there is no matching wavelengthλ in the first storage part 113, the control part 111 informs theoperator that the wavelength-setting operation has failed.

A fifth embodiment of the present invention will be described withreference to FIGS. 18 through 23. In the above-mentioned fourthembodiment, the optical signal is intensity modulated by controllingON/OFF states and therefore the optical signal is disconnected in theOFF state. The fifth embodiment is similar to the fourth embodimentexcept that encoding/modulation of a type that does not use an OFF stateis performed. That is to say, the intensity of the optical signal ischanged to such an extent that data contained in the optical signal isnot lost. Thus, the encoded and modulated signal for transferringλ-information can be generated without disconnecting the optical signalor without losing data that were originally contained in the opticalsignal.

In this embodiment, the λ-information data are generated by controllingthe light intensity levels of the optical signal between two levels,such as between Middle and High or between Middle and Low. Further, theλ-information data may be generated by controlling the light intensitylevels of the optical signal between three levels, such as Middle, Highand Low. Then, the generated λ-information data are transmitted from thewavelength interface subunit Bx to the wavelength-converting subunit Ax.To this end, each of the wavelength interface subunits Bx is providedwith an output level controlling part (OLC) 128 and the correspondingwavelength-converting subunit Ax is provided with an input leveldetecting part (ILD) 117. The input level detecting part 117 detects theMiddle and Low levels, Middle and High levels, or, Middle, Low and Highlevels to obtain the λ-information.

Requirements for the fifth embodiment are that the wavelength-convertingand wavelength interface units 110 and 120 are in their operationalstate and that the wavelength-converting unit 110 and the wavelengthinterface unit 120 are arranged so as to oppose each other.

The fifth embodiment differs from the fourth embodiment in that STARTDATA, END DATA and the λ-information data are not encoded and modulatedin a manner illustrated in FIGS. 15 through 17, but instead encoded andmodulated (without signal disconnections) as shown in FIG. 19 or 20A and20B, and FIGS. 21, 22, or 23.

In an example shown in FIG. 19, two levels of optical signal, i.e.,Middle and Low, or, Middle and High, are used. FIG. 21 shows an exampleof an encoding/modulation pattern using the Middle and Low levels. In anexample shown in FIG. 20A, three levels of optical signal, i.e., Middle,Low and High, are used. FIG. 22 shows an example of anencoding/modulation pattern using the three levels of optical signal.

FIG. 20B shows an example in which encoding and modulation is performedfor an intensity of light and a duration of a particular intensity. FIG.23 shows an example of an encoding/modulation pattern for such a case.In detail, for the example shown in FIG. 23, Middle level and fourvalues, i.e., High-Short, High-Long, Low-Short and Low-Long are used.

A sixth embodiment of the present invention will be described withreference to FIGS. 24 and 25. Conventionally, the wavelength interfaceunit 120 has an idle state to prevent it from being unintentionallyoperated. During the idle state, no data are output. When the operatorinputs an instruction to change into an operational state, thewavelength interface unit 120 starts outputting data.

The present embodiment relates to an operation in which, for the fourthand fifth embodiments described with reference to FIGS. 14 and 18, theoperator inputs an instruction into the wavelength interface unit 120for changing the wavelength interface unit Bx from the idle state to theoperational state so as to start the λ-setting processes. In otherwords, in response to an instruction from the operator, the control part121 controls the third encoder/modulator part 127 or the output levelcontrolling part 128 such that the optical signal is encoded andmodulated to transmit the λ-information the wavelength-convertingsubunit Ax of the wavelength-converting unit A. Thereafter, theλ-setting operation is performed in a manner similar to theabove-mentioned fourth and fifth embodiments.

A seventh embodiment of the present invention will be described withreference to FIGS. 26 and 27. In the above-described sixth embodiment,an instruction for changing from the idle state to the operational stateis made to the wavelength interface unit 120. Whereas, according to theseventh embodiment, such an instruction is made to thewavelength-converting unit 110. FIG. 26 shows a variant of the seventhembodiment in which a fourth encoder/modulator part 118 is provided inthe wavelength-converting subunit Ax of the wavelength-converting unit110 shown in FIG. 14. FIG. 27 shows a variant of the seventh embodimentin which an output level controlling part 211 is provided in thewavelength-converting unit 110 and an input level controlling part 251is provided in the wavelength interface unit 120.

An operation of the seventh embodiment will be described in detail.

First, the variant of the seventh embodiment shown in FIG. 26, whichcorresponds to the fourth embodiment, will be described. The operatorinputs a request (parameters: device name, channel name and operationalstate) for the wavelength-converting subunit Ax to change from an idlestate to an operational state. The control part 111 analyses the requestand controls the ON/OFF states of the optical signal at theencoder/modulator part 127 so as to transmit a λ-setting request data.The wavelength interface subunit Bx of the wavelength interface unit 120receives and decodes/demodulates the setting request data and obtainsthe relevant λ-setting instruction. Then, the wavelength interfacesubunit Bx reads the λ-information from the λ-information storage part126 and controls the encoder/modulator part 127 so as to modulate theoptical signal using the ON/OFF states to produce the START DATA and theλ-information. Then, the START DATA and the λ-information aretransmitted to the wavelength-converting subunit Ax of thewavelength-converting unit 110. Thereafter, a λ-setting operation isperformed in a manner similar to the fourth embodiment.

Next, another variant of the seventh embodiment shown in FIG. 27, whichcorresponds to the fifth embodiment, will be described. The operatorinputs a request (parameters: device name, channel name and operationalstate) for the wavelength-converting subunit Ax to change from an idlestate to an operational state. The control part 111 analyses the requestand intensity modulates the optical signal at the output levelcontrolling part 211 so as to transmit a λ-setting request data. Thewavelength interface subunit Bx of the wavelength interface unit 120receives and demodulates the setting request data at the input leveldetecting part 251 and obtains the relevant λ-setting instruction. Then,the wavelength interface subunit Bx reads the λ-information from theλ-information storage part 126 and controls the output level controllingpart 252 so as to intensity modulate the optical signal to produce theSTART DATA and the λ-information. Then, the START DATA and theλ-information are transmitted to the wavelength-converting subunit Ax ofthe wavelength-converting unit 110. Thereafter, a λ-setting operation isperformed in a manner similar to the fifth embodiment.

An eighth embodiment of the present invention will be described belowwith reference to FIGS. 28 and 29.

First, a variant of the eighth embodiment shown in FIG. 28, whichcorresponds to the embodiment shown in FIG. 14, will be described. Thewavelength interface subunit Bx of the wavelength interface unit 120 isfurther provided with a transmitter part 253 for transmittingλ-information data and the corresponding wavelength-converting subunitAx of the wavelength-converting unit 110 is provided with a receiverpart 213 for receiving the λ-information data. Further, acoupler/decoupler 214 made of optical couplers is provided on anupstream side of the wavelength-converting subunit Ax so as to decouplethe signal that is input from the wavelength interface subunit Bx andcouple the signal that is output to the wavelength interface subunit Bx.Also, a coupler/decoupler 254 made of optical couplers is provided on adownstream side of the wavelength interface subunit Bx so as to decouplethe signal that is input from the wavelength-converting subunit Ax andcouple the signal that is output to the wavelength-converting subunitAx.

Further, in order to generate λ-setting request data and send the datafrom the wavelength-converting subunit Ax to the wavelength interfacesubunit Bx, the wavelength-converting subunit Ax is further providedwith an encoder/modulator part 215. Also, in order to generateλ-information data and send the data from the wavelength interfacesubunit Bx to the wavelength-converting subunit Ax, the wavelengthinterface subunit Bx is further provided with an encoder/modulator part255. Further, in order to detect the λ-information data from thewavelength interface subunit Bx and obtain the λ-information, thewavelength-converting subunit Ax is further provided with anencoder/modulator part 216.

Next, another variant of the eighth embodiment shown in FIG. 29, whichcorresponds to the embodiment shown in FIG. 18, will be described. In amanner similar to the example shown in FIG. 28, a transmitter part 253for transmitting the λ-setting request data is provided in thewavelength interface subunit Bx and a receiver part 213 for receivingthe λ-setting request data is provided in the wavelength-convertingsubunit Ax. Further, a coupler/decoupler 214 made of optical couplers isprovided on an upstream side of the wavelength-converting subunit Ax soas to decouple the signal that is input from the wavelength interfacesubunit Bx and couple the signal that is output to the wavelengthinterface subunit Bx. Also, a coupler/decoupler 254 made of opticalcouplers is provided on an downstream side of the wavelength interfacesubunit Bx so as to decouple the signal that is input from thewavelength-converting subunit Ax and couple the signal that is output tothe wavelength-converting subunit Ax.

The wavelength-converting subunit Ax is further provided with an outputlevel controlling part 217 for generating and transmitting λ-settingrequest data from the wavelength-converting subunit Ax to the wavelengthinterface subunit Bx. The wavelength interface subunit Bx is furtherprovided with an input level detecting part 256 for detecting theλ-setting request data from the wavelength-converting subunit Ax and toobtain the λ-setting request. Further, the wavelength interface subunitBx is provided with an output level controlling part 257 for generatingand transmitting λ-information data from the wavelength interfacesubunit Bx to the wavelength-converting subunit Ax. Also, thewavelength-converting subunit Ax is provided with an input leveldetecting part 218 for detecting the λ-information data from thewavelength interface subunit Bx and to obtain the λ-information.

In the present invention, a requirement is that a signal λx-A (a signalhaving a wavelength from the wavelength-converting unit 110 to thewavelength interface unit 120) may assume a non-communicating stateuntil the automatic λ-setting operation is completed.

In the present embodiment, the wavelength λx-A of an output signal tothe upstream direction is automatically set in a manner described below.

In other words, when the operator changes the state of thewavelength-converting subunit Ax from an idle state to an operationalstate, the control part 111 of the wavelength-converting unit 110 sendsa λ-setting request to the encoder/modulator part 215 of thewavelength-converting subunit Ax in a case shown in FIG. 28 and to theoutput level controlling part 217 of the wavelength-converting subunitAx in a case shown in FIG. 29. The encoder/modulator part 215 or theoutput level controlling part 217 that has received the λ-settingrequest modulates (using ON/OFF levels or intensity modulation as in thefourth and fifth embodiments) the λ-setting request data and sends theλ-setting request data (of predetermined patterns).

The data processing part 126 (in the example of FIG. 28) or the inputlevel detecting part 256 (in the example of FIG. 29) that has receivedthe λ-setting request data from the wavelength-converting subunit Axtransmits the λ-setting request to the encoder/modulator part 255 or theoutput level controlling part 257 of the wavelength interface subunitBx.

Thereafter, in a manner similar to the fourth and fifth embodiments, theλ-information is transmitted from the wavelength interface subunit Bx tothe wavelength-converting subunit Ax via the signal λ1-A. Thewavelength-converting subunit Ax sets the received λ-information for itstransmitting part TX.

Thus, according to the eighth embodiment, a coupler/decoupler made ofoptical couplers is provided, and therefore, a bi-directional signalcommunication can be performed between the wavelength-convertingsubunits Ax and Bx via an optical transmission path. Accordingly, anefficient use of the optical transmission path (fiber optics) can beachieved.

Now, a ninth embodiment of the present invention will be described withreference to FIGS. 30 through 32.

In the present embodiment, the wavelength λ of the optical signalstransmitted from the wavelength interface unit 120 to thewavelength-converting unit 110 is analyzed and detected at thewavelength-converting unit 110 and the detected wavelength λ is set tothe transmitter part of the wavelength-converting unit 110.

In detail, the wavelength-converting unit 110 is provided with abranching unit 219 with which the received data are divided into twoparts. One part is connected to the prior art receiver part and theother part is input into a λ-analyzer 220 of the present invention. Inthis manner, the wavelength λ of the data received from the wavelengthinterface unit 120 is measured.

An operation of the ninth embodiment will be described with reference toa flowchart of FIG. 31.

In step S61, the operator inputs a data output request into thewavelength-converting unit 110. When the channel number and the λ-value(may also be unspecified) are passed to the control part 111, thecontrol part 111 analyses the request (step S62).

If it is determined that the λ-value is specified in the request (stepS63, YES), the specified λ-value is set to the transmitter part in aconventional manner (step S73).

On the other hand, if it is determined that the λ-value is not specifiedin the request (step S63, NO), it is determined whether the dataprocessing part 112 is currently receiving signals (step S64). If theresult indicates that the data processing part 112 is currently notreceiving signals (step S64, NO), the operator is informed that anautomatic setting has failed (informed of the channel number and areason of refusal) (step S66) and the process terminates.

If the result of step S64 indicates that the data processing part 112 iscurrently receiving the signals (step S64, YES), the λ-measuring part221 is activated and a λ-measurement request is sent (step S65). Theλ-measurement part 221 that has received the λ-measurement requestobtains from the λ-analyzer 220 the received λ-measurement value of therelevant reception signal (step S67).

Then, as will be described below, allowable ranges are added to thereceived λ-measurement value (lambda_measured) (step S68).

lambda_s=lambda_measured x (1−k)

lambda_l=lambda_measured x (1+k).

Then, the wavelength λ is sequentially read from the first wavelength λcontained in the first storage part (the values read out are stored in avariable lamda_enable). Then, as will be described below, a comparisonis made to determine whether this value is within the allowable rangeobtained in step S68 (step S69).

That is to say, it is determined whether:

lambda_s<lambda_enable, and,

lambda_enable<lambda_l.

If the result shows that there is a wavelength λ (lambda_enable) thatsatisfies the above conditions, the wavelength λ is set (step S72).Then, a data output request is sent to the control part 111. When thecontrol part 111 receives the data output request, it performs a processthat is similar to the above-described process and sets the wavelength λto the transmitter part TX.

Now, an operation will be described for a case in which after setting λaccording to the process described above, the signal transmission fromthe wavelength interface unit 120 to the wavelength-converting unit 110has halted for some reason. Such a case may be when there is a change ofwavelength to be used for transmission to the upstream side and thetransmission has interrupted temporarily.

It is determined whether the data processing part 112 has detected adata halt from the wavelength interface unit 120 (step S81). Then, thecontrol part 111 sends DATA OFF to the operator (step S82). If it isdetermined that the data processing part 112 has detected DATA ON thatindicates that signal reception from the wavelength interface unit 120is initiated (step S83, YES), the control part 111 send DATA ON to theoperator (step S84). In such a case, in order to determine whether thereis a change of the receiving wavelength λ of the signal, a λ-measurementrequest is sent to the λ-measuring part 221 (step S85).

The λ-measuring part 221 that has received the λ-measurement requestobtains the received λ-measurement value from the λ-analyzer 220 (stepS86). Then, in step S87, a predetermined allowable range k is added tothe received λ-measurement value (lambda_measured), as follows:

lambda_s=lambda_measured x (1−k)

lambda_l=lambda_measured x (1+k).

Then, it is compared and verified whether the current outputλ-measurement value (lambda_old) of the wavelength-converting unit 110is within the allowable range (step S88). That is to say, it isdetermined whether:

lambda_s<lambda_old, and,

lambda_old<lambda_l.

If the result indicates that the current output λ is within theallowable range (step S88, YES), it can be determined that λ has notbeen changed and the process is terminated. However, if the currentoutput λ is not within the allowable range (step S88, NO), λ is reset.

That is to say, the wavelength λ is read out from the first wavelength λstored in the first storage part 113 and then stored in variablelambda_enable (step S89). Then, it is compared whether the read outwavelength λ is within the allowable range (step S90). That is to say,it is determined whether:

lambda_s<lambda_enable, and,

lambda_enable<lambda_l.

If the result indicates that there is a wavelength λ (lambda_enable)that meets the above-conditions, it is set as a new wavelength λ (stepS92). Then, a λ-alteration request is sent to the control part 111. Thecontrol part 111 performs a conventional λ-alteration process (step S93)and the process terminates.

A variant of the ninth embodiment shown in FIG. 30 will be describedwith reference to FIG. 33.

As shown in FIG. 33, the wavelength-converting unit 110 is furtherprovided with an abnormality monitoring part 222. The abnormalitymonitoring part 222 monitors the λ-measuring part 221. If all trials forλ should fail (step S71, YES), the abnormality monitoring part 222informs the operator of the abnormality.

Also, if trials for λ should fail upon recovering from the DATA OFFstate to the DATA ON state (step S91, YES), the abnormality monitoringpart 222 sends a data output OFF request to the control part 111.

A tenth embodiment of the present invention will be described withreference to FIGS. 34 through 36.

The tenth embodiment is similar to the ninth embodiment shown in FIG. 30except that, instead of the λ-analyzer, a variable wavelength filter 224is provided in the wavelength-converting unit 110. A filter coefficient,i.e., pass band, of the variable wavelength filter 224 is sequentiallyaltered such that a wavelength λ that can be output is passed. In such amanner, the wavelength λ of the signal that is passed is detected bymeans of the variable wavelength filter 224.

That is to say, when the operator inputs a data output request inputinto the wavelength-converting unit 110 in step S101 of FIG. 35, steps101 through S105 are performed that are similar to the steps S61 throughS65 shown in FIG. 31.

After receiving the λ-measurement request, the λ-measurement part 221reads out the first wavelength λ stored in the first storage part 113and stores it in variable lambda_enable (step S107). The variablewavelength filter 224 is controlled such that the signal can passthrough only when its wavelength λ matches lambda_enable (step S108).After a certain time interval (e.g., five seconds) has elapsed (stepS111, YES), the variable wavelength filter 224 is controlled such thatthe next wavelength λ in the first storage part 113 is passed through(steps S107 and S108). Thereafter, the wavelength λ that is allowed topass through the variable wavelength filter 224 is changed at a constantinterval (a loop from steps S107 to S111).

Meanwhile, the data processing part 112 monitors the light intensitylevel of the received data. If it is determined that the received datahave passed through the variable wavelength filter 224 (step S109, YES),the setting value λ of the filter 224 is stored in lambda_ok (stepS112). Then, a data output request is sent to the control part 111.Then, the control part 111 performs the conventional λ specified dataoutput setting process (S113) and terminates the operation.

When recovering from DATA OFF to DATA ON, steps S121 through S125 thatare similar to the steps S81 through S85 of FIG. 32 are performed (seeFIG. 36). The λ-measuring part 221 that has received the λ-measuringrequest determines whether the received signal can pass through thevariable wavelength filter 224 at the current setting (steps S126). Ifthe received signal passes through the variable wavelength filter 224(steps S126, YES), λ has not been altered and the operation iscompleted. If it is determined that the received signal is not allowedto pass through the variable wavelength filter 224 (step S216, NO), thewavelength λ is reset.

In order to reset the wavelength λ, the λ-measuring part 221 that hasreceived the λ-measuring request controls the coefficient of thevariable wavelength filter 224 such that the first wavelength λ storedin the first storage part 113 (lambda_enable) is allowed to pass through(steps S127 and S128). After a predetermined time period (e.g., t=5[s])has elapsed (step S131, YES), the variable wavelength filter 224 iscontrolled such that the next wavelength λ is allowed to pass through(steps S127 and S128). Thereafter, the wavelength λ that is allowed topass through the variable wavelength filter 224 is changed at a constantinterval (a loop from steps S127 to S131).

Meanwhile, the data processing part 112 monitors the light intensitylevel of the received data. If it is determined that the received datahave passed through the variable wavelength filter 224 (step S129, YES),the setting value λ of the filter 224 is stored in lambda_ok (stepS132). Then, a request to change λ is sent to the control part 111.Then, the control part 111 performs the conventional λ changing process(step S133) and terminates the operation.

An eleventh embodiment of the present invention will be described withreference to FIGS. 37 and 38. In the prior art, the wavelength λ to beoutput to the upstream side of the wavelength-converting unit 110 isdetermined by varying the wavelength λ at the upstream output part ofthe wavelength-converting unit 110 such that the output wavelength λmatches a wavelength λ that is receivable at the wavelength interfacesubunit Bx of the opposing wavelength interface unit 120. In the presentembodiment, all wavelengths λ are output from the wavelength-convertingunit 110 (steps S141 and S142). All the wavelengths λ are coupled into asingle ray in the coupler/decoupler 225 and the single ray is outputfrom the upstream output part of the wavelength-converting unit 110(step S143). Also, the wavelength interface subunit Bx of the wavelengthinterface unit 120 is provided with a filter 258 at a positiondownstream of the receiving part. The filter 258 allows only awavelength λ unique to each wavelength interface subunit Bx to passthrough (step S144).

According to the eleventh embodiment, all of the wavelength-convertingsubunits Ax of the wavelength-converting unit 110 may be of the samestructure and also adjustment or setting of the wavelength λ is notnecessary.

Further, the present invention is not limited to these embodiments, andvariations and modifications may be made without departing from thescope of the present invention.

The present application is based on Japanese priority application No.2002-164675 filed on Jun. 5, 2002, the entire contents of which arehereby incorporated by reference.

1. A wavelength-division multiplexing (WDM) device comprising: amultiplexing part having a plurality of input terminals that are capableof receiving fixed wavelengths, respectively, and an output terminal,said fixed wavelengths being multiplexed onto a multiplexed signal andoutput via said output terminal; a wavelength-converting unit having aplurality of wavelength-converting parts each connected to an opticaltransmission device so as to convert an input wavelength from saidoptical transmission device into a converted wavelength corresponding tosaid fixed wavelength; a wavelength interface unit having a plurality ofinterface parts each connected between an input terminal of saidmultiplexing part and a wavelength-converting part, each said interfacepart having a specific wavelength that matches the fixed wavelength ofsaid input terminal of said multiplexing part; a filter within each saidinterface part that allows said specific wavelength to pass through anencoder/modulator that encodes and modulates the filtered signal into apattern specific to said interface part; and a detection unit thatdetects said specific wavelength of said interface part by sequentiallyaltering the converted wavelength, analyzing wavelengths of themultiplexed signal to detect said encoded and modulated signal wherefromsaid pattern specific to said interface part is obtained and identifyingsaid interface part and its specific wavelength.
 2. The WDM device asclaimed in claim 1, further comprising repeating means for repeating anoperation of detecting the fixed wavelengths of the connected outputterminal by sequentially altering the converted wavelength from saidwavelength-converting part; and outputting means for outputting a signalindicating an abnormal state when number of repetition exceeds apredetermined number.
 3. The WDM device as claimed in claim 1, furthercomprising a storage part within each wavelength-converting part inwhich information of the converted wavelength for thewavelength-converting part whose converted wavelength has already beendetermined is stored.
 4. The WDM device as claimed in claim 1, furthercomprising a coupler/decoupler for said plurality ofwavelength-converting parts and a coupler/decoupler for said pluralityof interface parts so as to enable signal communication between saidplurality of wavelength-converting parts and said plurality of interfaceparts using a single transmission path.
 5. A wavelength-divisionmultiplexing (WDM) device comprising: a multiplexing part having aplurality of input terminals that are capable of receiving fixedwavelengths, respectively, and an output terminal, said fixedwavelengths being multiplexed onto a multiplexed signal and output viasaid output terminal; a wavelength-converting unit having a plurality ofwavelength-converting parts each connected to an optical transmissiondevice so as to convert an input wavelength from said opticaltransmission device into a converted wavelength corresponding to saidfixed wavelength; a wavelength interface unit having a plurality ofinterface parts each connected between an input terminal of saidmultiplexing part and a wavelength-converting part, each said interfacepart having a specific wavelength that matches the fixed wavelength ofsaid input terminal of said multiplexing part; an encoder/modulatorwithin each said interface part that encodes and modulates an opticalsignal in a pattern specific to said specific wavelength and saidinterface part transmits the encoded and modulated optical signal to thewavelength-converting part connected thereto; and a detection unit thatdetects said specific wavelength of said interface part by reading saidspecific wavelength from a modulated component of said encoded andmodulated optical signal.
 6. The WDM device as claimed in claim 5,wherein said encoder/modulator encodes and modulates the optical signalby stopping and restarting the transmission of the optical signal at apredetermined timing specific to the relevant interface part such thatthe interface parts can be uniquely and individually identified.
 7. TheWDM device as claimed in claim 5, wherein said encoder/modulator encodesand modulates the optical signal by altering the intensity of theoptical signal at a predetermined timing specific to the relevantinterface part such that the interface parts can be uniquely andindividually identified.
 8. The WDM device as claimed in claim 5,wherein information of the specific wavelength of the interface part isreported by modulating said optical signal and an operation of detectingthe specific wavelength at the wavelength-converting part is initiatedby an operational input by an operator.
 9. The WDM device as claimed inclaim 5, further comprising a coupler/decoupler for said plurality ofwavelength-converting parts and a coupler/decoupler for said pluralityof interface parts so as to enable signal communication between saidplurality of wavelength-converting parts and said plurality of interfaceparts using a single transmission path.
 10. A wavelength-divisionmultiplexing (WDM) device comprising: a multiplexing part having aplurality of input terminals that are capable of receiving fixedwavelengths, respectively, and an output terminal, said fixedwavelengths being multiplexed onto a multiplexed signal and output viasaid output terminal; a wavelength-converting unit having a plurality ofwavelength-converting parts each connected to an optical transmissiondevice so as to convert an input wavelength from said opticaltransmission device into a converted wavelength corresponding to saidfixed wavelength; and a wavelength interface unit having a plurality ofinterface parts each connected between an input terminal of saidmultiplexing part and a wavelength-converting part, each said interfacepart having a specific wavelength that matches the fixed wavelength ofsaid input terminal of said multiplexing part, a detection unit thatdetects said specific wavelength of each said interface part by eachsaid interface part transmitting optical signals of said specificwavelength to the wavelength-converting part connected thereto, and saidwavelength-converting part analyzes the wavelength of the transmittedoptical signal to detect the specific wavelength of said interface part.11. The WDM device as claimed in claim 10, further comprising means forgenerating a signal indicating an abnormal state if the wavelength valueobtained by said analysis is not within the configurable wavelengthrange of said wavelength-converting part.
 12. The WDM device as claimedin claim 10, further comprising a coupler/decoupler for said pluralityof wavelength-converting parts and a coupler/decoupler for saidplurality of interface parts so as to enable signal communicationbetween said plurality of wavelength-converting parts and said pluralityof interface parts using a single transmission path.
 13. A method ofautomatically setting a converted wavelength output from each of aplurality of wavelength-converting parts of a wavelength-divisionmultiplexing (WDM) device, said WDM device including: a multiplexingpart having a plurality of input terminals that are capable of receivingfixed wavelengths, respectively, and an output terminal, said fixedwavelengths being multiplexed onto a multiplexed signal and output viasaid output terminal; a wavelength-converting unit having a plurality ofwavelength-converting parts each connected to an optical transmissiondevice so as to convert an input wavelength from said opticaltransmission device into a converted wavelength corresponding to saidfixed wavelength; a wavelength interface unit having a plurality ofinterface parts each connected between an input terminal of saidmultiplexing part and a wavelength-converting part, each said interfacepart having a specific wavelength that matches the fixed wavelength ofsaid input terminal of said multiplexing part; a filter within each saidinterface part that allows said specific wavelength to pass through anencoder/modulator that encodes and modulates the filtered signal into apattern specific to said interface part; and a detection unit thatdetects said specific wavelength of said interface part by sequentiallyaltering the converted wavelength, analyzing wavelengths of themultiplexed signal to detect said encoded and modulated signal wherefromsaid pattern specific to said interface part is obtained and identifyingsaid interface part and its specific wavelength.
 14. Awavelength-division multiplexing (WDM) device comprising: a multiplexingpart having a plurality of input terminals that are capable of receivingfixed wavelengths, respectively, and an output terminal, said fixedwavelengths being multiplexed onto a multiplexed signal and output viasaid output terminal; a wavelength-converting unit having a plurality ofwavelength-converting parts each connected to an optical transmissiondevice so as to convert an input wavelength from said opticaltransmission device into a converted wavelength corresponding to saidfixed wavelength; a wavelength interface unit having a plurality ofinterface parts each connected between an input terminal of saidmultiplexing part and a wavelength-converting part, each said interfacepart having a specific wavelength that matches the fixed wavelength ofsaid input terminal of said multiplexing part; and a determination unitthat determines said specific wavelength of said interface part by saidinterface part transmitting optical signals of its specific wavelengthto the wavelength-converting part connected thereto, and said opticalsignals of the specific wavelength being supplied to a variablewavelength filter provided in said wavelength-converting part whilevarying the pass-band wavelength of said variable wavelength filter soas to obtain the pass-band wavelength of said filter when said opticalsignal is allowed to pass through.
 15. The WDM device as claimed inclaim 14, further comprising means for generating a signal indicating anabnormal state if the signal from said interface part does not passthrough said variable wavelength filter even if the pass-band of saidvariable wavelength filter has been altered.
 16. The WDM device asclaimed in claim 14, further comprising a coupler/decoupler for saidplurality of wavelength-converting parts and a coupler/decoupler forsaid plurality of interface parts so as to enable signal communicationbetween said plurality of wavelength-converting parts and said pluralityof interface parts using a single transmission path.
 17. A methodcomprising: automatically setting a converted wavelength output fromeach of a plurality of wavelength-converting parts of awavelength-division multiplexing (WDM) device, said WDM devicecomprising: a multiplexing part having a plurality of input terminalsthat are capable of receiving fixed wavelengths, respectively, and anoutput terminal, said fixed wavelengths being multiplexed onto amultiplexed signal and output via said output terminal; awavelength-converting unit having a plurality of wavelength-convertingparts each connected to an optical transmission device so as to convertan input wavelength from said optical transmission device into aconverted wavelength corresponding to said fixed wavelength; awavelength interface unit having a plurality of interface parts eachconnected between an input terminal of said multiplexing part and awavelength-converting part, each said interface part having a specificwavelength that matches the fixed wavelength of said input terminal ofsaid multiplexing part; an encoder/modulator within each said interfacepart that encodes and modulates an optical signal in a pattern specificto said specific wavelength and said interface part transmits theencoded and modulated optical signal to the wavelength-converting partconnected thereto; and a detection unit that detects said specificwavelength of said interface part by reading said specific wavelengthfrom a modulated component of said encoded and modulated optical signal.18. A method comprising: automatically setting a converted wavelengthoutput from each of a plurality of wavelength-converting parts of awavelength-division multiplexing (WDM) device, said WDM devicecomprising: a multiplexing part having a plurality of input terminalsthat are capable of receiving fixed wavelengths, respectively, and anoutput terminal, said fixed wavelengths being multiplexed onto amultiplexed signal and output via said output terminal; awavelength-converting unit having a plurality of wavelength-convertingparts each connected to an optical transmission device so as to convertan input wavelength from said optical transmission device into aconverted wavelength corresponding to said fixed wavelength; awavelength interface unit having a plurality of interface parts eachconnected between an input terminal of said multiplexing part and awavelength-converting part, each said interface part having a specificwavelength that matches the fixed wavelength of said input terminal ofsaid multiplexing part; and a determination unit that determines saidspecific wavelength of said interface part by said interface parttransmitting optical signals of its specific wavelength to thewavelength-converting part connected thereto, and said optical signalsof the specific wavelength being supplied to a variable wavelengthfilter provided in said wavelength-converting part while varying thepass-band wavelength of said variable wavelength filter so as to obtainthe pass-band wavelength of said filter when said optical signal isallowed to pass through.
 19. A method of automatically setting aconverted wavelength output from each of a plurality ofwavelength-converting parts of a wavelength-division multiplexing (WDM)device, the method comprising: receiving fixed wavelengths at aplurality of input terminals of a multiplexing part of the WDM deviceand multiplexing the fixed wavelengths onto a multiplexed signal that isoutput via an output terminal of the WDM device; converting an inputwavelength, from an optical transmission device that is connected toeach of a plurality of wavelength-converting parts of awavelength-converting unit of the WDM device, into a convertedwavelength corresponding to the fixed wavelength; connecting a pluralityof interface parts of a wavelength interface unit of the WDM devicebetween an input terminal of the multiplexing part of the WDM device anda wavelength-converting part of the WDM device, each interface parthaving a specific wavelength that matches the fixed wavelength of theinput terminal of the multiplexing part; encoding and modulating anoptical signal in a pattern specific to the specific wavelength, theinterface part transmitting the encoded and modulated optical signal tothe wavelength-converting part connected thereto; and detecting thespecific wavelength of the interface part by reading the specificwavelength from a modulated component of the encoded and modulatedoptical signal.
 20. A method of automatically setting a convertedwavelength output from each of a plurality of wavelength-convertingparts of a wavelength-division multiplexing (WDM) device, the methodcomprising: receiving fixed wavelengths at a plurality of inputterminals of a multiplexing part of the WDM device and multiplexing thefixed wavelengths onto a multiplexed signal that is output via an outputterminal of the WDM device; converting an input wavelength, from anoptical transmission device that is connected to each of a plurality ofwavelength-converting parts of a wavelength-converting unit of the WDMdevice, into a converted wavelength corresponding to the fixedwavelength; connecting a plurality of interface parts of a wavelengthinterface unit of the WDM device between an input terminal of themultiplexing part of the WDM device and a wavelength-converting part ofthe WDM device, each interface part having a specific wavelength thatmatches the fixed wavelength of the input terminal of the multiplexingpart; and determining the specific wavelength of the interface part bythe interface part transmitting optical signals of the specificwavelength to the wavelength-converting part connected thereto, theoptical signals of the specific wavelength being supplied to a variablewavelength filter provided in the wavelength-converting part whilevarying the pass-band wavelength of the variable wavelength filter so asto obtain the pass-band wavelength of the filter when the optical signalis allowed to pass through.
 21. A method of automatically setting aconverted wavelength output from each of a plurality ofwavelength-converting parts of a wavelength-division multiplexing (WDM)device, said WDM device including: a multiplexing part having aplurality of input terminals that are capable of receiving fixedwavelengths, respectively, and an output terminal, said fixedwavelengths being multiplexed onto a multiplexed signal and output viasaid output terminal; a wavelength-converting unit having a plurality ofwavelength-converting parts each connected to an optical transmissiondevice so as to convert an input wavelength from said opticaltransmission device into a converted wavelength corresponding to saidfixed wavelength; and a wavelength interface unit having a plurality ofinterface parts each connected between an input terminal of saidmultiplexing part and a wavelength-converting part, each said interfacepart having a specific wavelength that matches the fixed wavelength ofsaid input terminal of said multiplexing part, a detection unit thatdetects said specific wavelength of each said interface part by eachsaid interface part transmitting optical signals of said specificwavelength to the wavelength-converting part connected thereto, and saidwavelength-converting part analyzes the wavelength of the transmittedoptical signal to detect the specific wavelength of said interface part.